Craft Gourmet Coffee Beans with a Homemade Roaster

Schematic and photos by Karl Rabe

Roasting your own gourmet coffee beans takes work and time, but turning green coffee beans into fragrant brown java can be addictive. Some home roasters do it for the cost savings; others because fresh coffee beats store bought any day; and still others because they love the challenge of the DIY process.

One of the easiest ways to roast small quantities is to use an air popcorn popper. Not all poppers work, but you can find rather inexpensive ones at Target.

To roast large quantities with a variety of flavor, read on for a step-by-step guide to turning your backyard gas grill into a heavy-duty roaster. Photos are courtesy of my engineer brother Karl Rabe, who sent out packaged beans as heavenly Christmas presents. His wife Patty added homemade biscotti biscuits for the perfect gift combination.

Warning, this is a DIY project designed for those who are truly handy. Don't take it on if you're looking for a 20-minute, project. (There's a reason Karl is an engineer.)

finished drum

1. Buy the perfect-sized stainless-steel canister for just $10 to serve as your drum. You'll also need a stainless-steel bowl with a flat bottom. Remove the bottom from the bowl and rivet it over the canister.

open-end design

2. This open-end design makes dumping the beans relatively hassle-free and allows you to see and sample the beans during processing. The collar on the rod retains the drum at this end.

prongs attached to drum

3. Use the prongs from a rotisserie kit to attach the drum to the rod. We recommend buying a Weber kit.

Weber kit

4. Your Weber rotisserie kit from Lowes will include a motor, rod and prongs. (The motor twirls the drum while the beans are roasting.)


5. A small thermocouple monitors the temperature inside the drum. Karl recommends buying one from with the 113 to 382 high-temp probe.

6. Follow the schematic in the lead photograph to assemble the kit with the drum.


7. The original rotisserie motor clocked in at about 6 rpm but Karl upgraded to a 60 rpm servo gear motor for $40. He also later added a metal shell to the motor for weather protection.


8. Preheat the grill on high. Place up to a pound of green beans into the roasting drum and put the drum on the grill. Position the thermocouple, turn on the motor and monitor the roast by sight and smell.

The beans will take between eight and 20 minutes to roast depending on the “roast” you desire. They will progress through the following process:

    • Yellowing: For the first few minutes the beans remain greenish, then turn lighter yellowish and emit a grassy smell.
    • Steam: The beans start to steam as their internal water content dissipates.
    • First Crack: The steam becomes fragrant. Soon you'll hear the "first crack," an audible cracking sound as the real roasting starts. Sugars begin to caramelize, bound-up water escapes, the structure of the bean breaks down and oils migrate from their little pockets outward. First crack sounds like popcorn popping.
    • First Roasted Stage: The roast can now be considered complete at any point, according to your taste. The cracking is an audible cue and, along with sight and smell, tells you what stage the roast has reached. This stage is what is known as a "City" roast.
    • Caramelization: Caramelization continues, oils migrate, and the bean expands in size as the roast becomes dark. As the roast progresses, this is a City-plus roast. When you are on the verge of second crack, it's deemed a "Full City" roast.
    • Second Crack: At this point a "second crack" can be heard, which sounds like Rice Crispies when you pour milk on top. The roast character starts to eclipse the origin character of the beans at this point. A few pops into second crack is a Full City-plus roast. A roast all the way through second crack is a Vienna roast.
    • Darkening Roast: As the roast becomes very dark, the smoke is more pungent as sugars burn completely and the bean structure continues to break down. This is a French roast.
    • NOT TOO FAR! Eventually, the sugars burn completely, and the roast will only result in thin-bodied cup of "charcoal water." The beans can actually catch on fire at this point, so be keep a watchful eye on the process.

wire basket with beans

10. Dump the roasted beans into a large wire basket.


11. A cheap box fan will both cool the beans and blow away extraneous chaff. Place the fan on top of several bricks for aeration and the basket on top of the fan. Stir the beans or shake the basket to agitate them for one or two minutes until they are cool to the touch.

12. Store the beans in an airtight container and repeat the process every two weeks or as desired.

For more detailed information and a larger schematic, visit Karl's explanatory website.

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1 Comment

What a great idea! I'm sure that took some thinking to come up with that.
Posted by James lackey